present invention relates to a thermostatic valve for a cooling system of an internal-combustion engine comprising a thermostatic working element which has a housing containing an expansion material which drives a working piston out of the housing as a function of the temperature and therefore, as a function of the temperature of a coolant, sets the positions of a main valve disk and of a short-circuit valve disk which bound a mixing chamber for coolant which flows in from a radiator through a main valve and for coolant which flows in directly from the internal-combustion engine through a short-circuit valve and is then returned to the internal-combustion engine.
In a thermostatic valve of the above described type shown German Patent Document DE-AS 12 95 255, the working piston of the thermostatic working element is supported in a stationary manner. The housing of this working element carries a main valve disk and a short-circuit valve disk. The housing of the thermostatic working element, which is the temperature sensing element, is situated completely in the mixing chamber which is bounded essentially by the main valve disk and the short-circuit valve disk. When the cold internal-combustion engine is started, this temperature sensing element is acted upon by the heating-up short-circuit flow of the cooling liquid so that the temperature sensing element opens up when this short-circuit flow has reached a defined temperature which is indicated by the selection of the expansion material (wax mixture).
It is an object of the invention to improve the control action of a thermostatic valve of the initially described type particularly during the starting of the cold internal-combustion engine of a motor vehicle.
This and other objects are achieved by the present invention which provides that the housing of the working element is held in a stationary manner, and that the working piston is equipped with the main valve disk. This main valve disk surrounds the housing of the working element in the manner of a pot and is provided with openings in the area of its side walls, and with the short-circuit valve disk. The main valve disk is guided, at least in the area of its closing position, in a sealing manner on the housing of the thermostatic working element or a holder of this housing. On the side of the main valve disk facing away from the working piston, the housing of the working element is disposed at least partially free in the coolant flowing in from the radiator.
With the present invention, the influence of very low outside temperatures and resulting correspondingly low radiator return flow temperatures is taken into account to an increased extent, particularly during the start of the internal-combustion engine. Since the temperature sensing element, specifically the housing of the thermostatic working element, is partially disposed in the cold coolant, a mixing temperature is obtained in the housing which is surrounded by the heating-up short-circuit flow so that the opening-up of the thermostatic valve is delayed at very low outside temperatures. As a result, it is achieved that a higher operating temperature is adjusted. Since the housing of the thermostatic working element is held in a stationary manner and does not move with the main valve disk into the area of the mixing chamber, the influence of very low outside temperatures and therefore of correspondingly low temperatures in the radiator return flow is taken into account to a greater extent also during the operating condition. A higher temperature level for the operating temperature is therefore set in the partial load range when the outside temperatures are low. In this manner, it is achieved that the thermostatic valve is automatically adjusted to a summer or winter operation. In the winter and at low outside temperatures, a higher temperature level is set in the partial load operation so that the comfort for the vehicle heater is also increased which is provided with a higher heating temperature.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.